Introduction
Lung functioning is a complex process involving many physiological components. Often, these processes are described using gas laws. Identification of principles, terminology regarding volumes and capacity, differences in men and women, and analysis of this process in its entirety are the goals of this work, where, among other things, gas laws and their formulas will be described for a better understanding of the functioning of the lungs.
Term Definitions
Lung Volumes and Capacities
Figure 1 presents many terms that reflect different lung volumes. As a rule, each person is unique regarding the average values of the listed capacities and volumes. However, long-term studies have shown that there are significant differences only between the sexes, men and women, and for each of these values (Des Jardins, 2012). These data were compiled into Table 1, which contains typical values for the listed indicators depending on gender. The following table interprets each term.
Table 1 – Lung Volumes and Capacities by Gender.
Tidal volume is inhaled and exhaled when a person is resting or exercising regularly. Total lung capacity is the maximum volume of air that the lungs can hold after a maximum inhalation. Vital capacity is similar to the previous term but implies the maximum possible volume that can be exhaled after inhalation. Inspiratory reserve volume describes the maximum volume of air forcibly inhaled after a normal inhalation.
On the contrary, expiratory reserve volume involves forced exhalation after normal exhalation. Residual volume assumes the maximum air volume remaining in the lungs after maximum exhalation, while functional residual volume is after normal exhalation.
Finally, forced expiratory volume in 1 second (FEV1) is the relative value of the forced expiratory air volume after maximum inspiration (Des Jardins, 2012). Because normal inhalation and exhalation ordinarily last less than a second, the forced one will be much faster, which is why the indicators of the latter value are the largest in the table—maximum voluntary expiration – absolute value for the relative indicator FEV1.
Gas Laws
Boyle’s Law
As stated above, the lungs’ functioning is described by several gas laws. For example, Boyle’s law, which states that at a constant temperature, the pressure exerted by a gas is inversely proportional to its volume, can be applied in this case. During inhalation, the diaphragm contracts, increasing the volume of the thoracic cavity and decreasing thoracic pressure, which forces air into the lungs (Kendrick, 2020).
Charles’s Law
Charles’s law suggests that at constant pressure, the volume of a gas is directly proportional to its absolute temperature – a similar condition can be encountered when a person exercises or has an elevated body temperature: the air in the lungs will expand due to temperature.
Dalton’s Law
Dalton’s law states that the total pressure exerted by a mixture of gases is equal to the sum of the partial pressures of each gas. This law applies to lung function as it regulates gas exchange in the alveoli (Kendrick, 2020). The partial pressure of oxygen or PO2 in the alveoli is higher than in the blood, causing oxygen to diffuse into the bloodstream.
Henry’s Law
Henry’s law describes another pattern in the functioning of the lungs. It states that the amount of gas dissolved in a liquid is directly proportional to the partial pressure of that gas above the liquid. Henry’s Law applies to lung function as it describes the exchange of gases between the alveoli and the bloodstream (Kendrick, 2020). Oxygen dissolves in the blood plasma and binds to hemoglobin; carbon dioxide dissolves in the plasma and forms bicarbonate ions.
Graham’s Law
Finally, Graham’s law, which postulates an inverse proportionality between the rate of diffusion of a gas and the square root of its molar mass, also describes lung processes. It affects the diffusion of gases across the respiratory membrane: lighter gases, such as oxygen, diffuse faster than heavier gases, such as carbon dioxide (Kendrick, 2020)—table 2 below shows the formulas for these laws.
Table 2 – Gas Laws.
Conclusion
This work provides an overview of the basic terms relating to lung volumes and capacities and gas laws that can describe the functionality of this part of the body. Such an analysis can serve as the basis for various research in respiratory physiology. However, it is worth keeping in mind that the functionality of the lungs is not limited to a physical description but is a complex phenomenon at the intersection of biology, anatomy, chemistry, and physics. A detailed study of such issues requires a comprehensive look at this body.
References
Des Jardins, T. (2012). Cardiopulmonary Anatomy & Physiology: Essentials of Respiratory Care. Cengage Learning.
Kendrick, A. (2020). Basic terminology and gas laws. Cotes’ Lung Function, 75-90. Web.
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